What happens to the anode when copper(II) sulfate solution is electrolysed using copper electrodes?

It dissolves and loses mass, because copper atoms lose electrons and enter the solution as Cu²⁺ ions.

What happens to the cathode when copper(II) sulfate solution is electrolysed using copper electrodes?

It gains mass, because copper is deposited on it.

The blue colour of copper(II) sulfate solution fades with inert electrodes but not with copper electrodes. Explain why.

With copper electrodes the anode dissolves and replaces the copper ions removed at the cathode, so the concentration stays the same.

How are non-inert electrodes used to purify copper?

The impure copper is used as the anode and dissolves, and pure copper is deposited on a pure copper cathode.

OCR GCSE Combined Science Chemistry J250

Chemical Reactions

Topic overview Writing formulae of elements and compounds Balanced equations, and deducing formulae from ions Ionic equations, and state symbols The mole and the Avogadro constant Conservation of mass, and changes of mass in open systems Stoichiometry, and calculating reacting masses Exothermic and endothermic reactions, and reaction profiles Activation energy, and bond energy calculations Oxidation and reduction, by oxygen and by electrons Acids, alkalis and neutralisation The ionic equation for neutralisation, and reactions of acids Dilute and concentrated, weak and strong The pH scale, and hydrogen ion concentration pH as a factor of ten, and measuring pH Products at the electrodes, and molten ionic compounds Electrolysis of aqueous solutions Inert and non-inert electrodes

Elements, Compounds and Mixtures

Topic overview Purity, and melting point data Relative formula mass and empirical formulae Formulations, and separating mixtures Paper and thin layer chromatography Interpreting chromatograms and Rf values Choosing a purification method Metals and non-metals in the Periodic Table Electron arrangement and position in the Periodic Table Ionic, covalent and metallic bonding compared Dot and cross diagrams, and the limits of models Reactions, electron arrangement and Mendeleev's table Carbon's four bonds, and the variety of organic compounds Diamond, graphite, fullerenes and graphene Bond strength, intermolecular forces and predicting state Bulk properties of ionic, molecular and giant structures

Global Challenges

Topic overview Extracting metals by reduction and by electrolysis Biological methods of metal extraction Life cycle assessment Recycling, and the decisions behind it Fractional distillation of crude oil The fractions, and crude oil as a feedstock Dependence on hydrocarbons, and cracking The Earth's early atmosphere, and how oxygen developed The greenhouse effect, and evidence for climate change Effects of carbon dioxide and methane, and air pollutants Producing potable water

Monitoring and Controlling Chemical Reactions

Topic overview Mass of solute, concentration and dilution calculations Measuring the rate of a reaction, and rate graphs Factors affecting rate, and collision theory Surface area and rate Catalysts and how they work Reversible reactions and dynamic equilibrium Changing the conditions of an equilibrium Activation energy, and enzymes as catalysts

Particles

Topic overview The particle model and changes of state Limitations of the particle model How the atomic model changed, and the structure of the atom The size of atoms, and the subatomic particles Calculating protons, neutrons and electrons

Predicting and Identifying Reactions

Topic overview Groups 1, 7 and 0, and why they behave as they do Predicting reactivity from the Periodic Table Reactivity of metals with water and acids Tests for oxygen, hydrogen, carbon dioxide and chlorine

Chemical Reactions

Inert and non-inert electrodes

2 things to know
Paper 9 (Chemistry)

Overview

Graphite and platinum as inert electrodes, what a non-inert electrode is, how copper electrodes change in copper(II) sulfate solution, purifying copper, setting up the cell, and why direct current is used.

What you need to know

Answer each one before you reveal it.

Your recallNot started

Key term

Which two materials are usually chosen for inert electrodes, and why?

Key term

What is a non-inert electrode?

Questions from this subtopic

Each one with the model answer underneath.

1
Which two materials are usually chosen for inert electrodes, and why?
Model answer
Graphite and platinum, because they conduct electricity well but do not react during the electrolysis.
2
What is a non-inert electrode?
Model answer
An electrode made of a material that takes part in the reaction and so changes during the electrolysis.
3
What happens to the anode when copper(II) sulfate solution is electrolysed using copper electrodes?
Model answer
It dissolves and loses mass, because copper atoms lose electrons and enter the solution as Cu²⁺ ions.
4
What happens to the cathode when copper(II) sulfate solution is electrolysed using copper electrodes?
Model answer
It gains mass, because copper is deposited on it.
5
The blue colour of copper(II) sulfate solution fades with inert electrodes but not with copper electrodes. Explain why.
Model answer
With copper electrodes the anode dissolves and replaces the copper ions removed at the cathode, so the concentration stays the same.
6
How are non-inert electrodes used to purify copper?
Model answer
The impure copper is used as the anode and dissolves, and pure copper is deposited on a pure copper cathode.

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Chemical Reactions

Elements, Compounds and Mixtures

Global Challenges

Monitoring and Controlling Chemical Reactions

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